I stopped maintaining the VadCalc applet. It was written in a weird little language called CA Realizer (Computer Associates), which I also used to write tubing movement programs for the oil and gas industry. I do most of my programming in C++, but that language was easier to use for some things, so I gave it a go for a while.I assume you want to use it because you don't want to build a box to find Vas with the sealed box method. If that's the case, I suggest the added mass method. Then again, I understand the desire to have a method that works without two impedance sweeps. The VadCalc process was simple to do, and provided a pretty good estimate of Vas.
Here's a formula that you can use to calculate Vas, knowing efficiency n0, Qes and fs:
More woofers specs list the SPL output at 1W/1M than reference efficiency, so here's a converter:
These days, I use Keith Larson's Woofer Tester and Speaker Tester products. They really make life easier. It has evolved a long way since the original Woofer Tester that he used to sell through Parts Express. You can use it to do acoustic measurements and make a digital crossover using Spice models to simulate passive crossovers. It's a great tool. And it still does the T/S measurements.
If you want to find T/S specs making measurements manually, or if you want to calculate values from other known values, here's a list of formulas that can be used to solve pretty much whatever you want to find:
Speaker system total Q at fc
α constant
Speaker total Q at fs
Efficiency/bandwidth product
Resonant frequency
Electrical Q
System resonant frequency
System total Q at fc
Resonant frequency
Speaker total Q at fs
Half power frequency (-3dB point)
System resonant frequency
Internal box volume
Compliance
Free air reference efficiency
Speaker resonant frequency
Compliance
Speaker electrical Q
Sound pressure level
Free air reference efficiency
Maximum air volume displaced by cone excursion
Peak linear displacement
Diaphragm radiating area
Volume displaced at Xmax
Diaphragm effective radiating diameter
Diaphragm radiating area
K1 constant
Air density
System resonant frequency
Volume displaced at Xmax
Speed of sound
K2 constant
K1 constant
Amax constant
Maximum displacement limited power output
K1 constant
Amax constant
Required electrical input to achieve Par
Maximum displacement limited power output
Free air reference efficiency
Peak sound pressure level
Maximum power input
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